Derivation and external validation of a risk score for clinically important declines in health and function among two longitudinal cohorts of women in the mid-life

OBJECTIVES: Women in mid-life often develop chronic conditions and experience declines in physical health and function. Identifying factors associated with declines provides opportunity for targeted interventions. We derived and externally validated a risk score for clinically important declines over 10 years among women ages 55–65 using the Physical Component Summary Score (PCS) of the SF-36. DESIGN: Derivation and validation of a risk score. SETTING: Two longitudinal cohorts from sites in the USA were used. PARTICIPANTS: Women from the Study of Women’s Health Across the Nation (SWAN) and women from the Women’s Health Initiative (WHI) Observational Study and/or clinical trials. OUTCOME MEASURES: A clinically important decline over 10 years among women ages 55–65 using the PCS of the SF-36 predictors was measured at the beginning of the 10 years of follow-up. RESULTS: Seven factors—lower educational attainment, smoking, higher body mass index, history of cardiovascular disease, history of osteoarthritis, depressive symptoms and baseline PCS level—were found to be significant predictors of PCS decline among women in SWAN with an area under the curve (AUC)=0.71 and a Brier Score=0.14. The same factors were associated with a decline in PCS in WHI with an AUC=0.64 and a Brier Score=0.18. Regression coefficients from the SWAN analysis were used to estimate risk scores for PCS decline in both cohorts. Using a threshold of a 30% probability of a significant decline, the risk score created a binary test with a specificity between 89%–93% and an accuracy of 73%–79%. CONCLUSIONS: Seven clinical variables were used to create a valid risk score for PCS declines that was replicated in an external cohort. The risk score provides a method for identifying women at high risk for a significant mid-life PCS decline.